Teaching machine

ABSTRACT

A movable record, such as a magnetic tape stores instructional items in paragraph form; associated with each instructional item is a code, recorded on the tape, indicative of a correct answer. A student-operated keyboard is provided which, upon depression of a key indicative of the correct answer, as instructed by the instructional item recorded on the tape, will provide a signal which is compared with a signal derived from the code recorded on the tape and, upon coincidence, causes the tape to proceed to the next instructional item. Upon non-coincidence, an&#39;&#39;&#39;&#39;error response&#39;&#39;&#39;&#39; is indicated; the next, or a subsidiary instructional item will be displayed to the student when a predetermined number of incorrect answers has been counted. The ends of items and switch-over of mode of the receiver (from sound for the student to decoding) is controlled by a special frequency recorded on the tape.

United States Patent n51 3,660,912

Laplume 1 1 May 9, 1972 [s41 TEACHING MACHINE 3,504,447 4/1970 Brudner..35/9 [72] Inventor: Jacques plume, GiflsuFYvem France 3,553,852 l/1971 Dorsett ..35/9 R [73] Assignee: Soclete D'Etudes Techniques et DEn-Primary -f Gfieb treprises Generales SODETEG, LePlessis- Attorney-Flynn81 Fmhfluf Robinson, France [57] ABSTRACT [22] Filed: Nov. 26, 1969 Amovable record, such as a magnetic tape stores instructional PP' N05880,144 items in paragraph form; associated with each instructional itemis a code, recorded on the tape, indicative of a correct answer. Astudent-operated keyboard is provided which, upon [30] ForeignApplication Priority Dam depression of a key indicative of the correctanswer, as in- Nov. 26, 1968 France ..l75325 structed by theinstructional item recorded on the tape. will provide a signal which iscompared with a signal derived from 52 us. Cl. ..3s/9 A the coderecorded on the p an up nc dence, ca e [51] Int. Cl, the tape to proceedto the next instructional item. Upon non- [58] new of Search ..35/9, 93,9 A coincidence. aw'mr response" is indicated; the next, or asubsidiary instructional item will be displayed to the student 56References Cited when a predetennined number of incorrect answers hasbeen 1 counted. The ends of items and switch-over of mode of the UNITEDSTATES PATENTS receiver (from sound for the student to decoding) iscontrolled by a special frequency recorded on the tape. 3,210,86410/1965 Tillotson ..35/9 3,383,781 5/1968 Diuzet ..35/9l2CIn1ms,8Drawingl-lgures MEMORY AND GATES RAL III. 7 RM. SHlFT REG aman am COUNTER 9. 2 1- m 24 21 1s Eran/111571 COUNlE AND PATEN'IEBMM91912 3.660.912

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TEACHING MACHINE RELATED APPLICATION U.S. Ser. No. 832,290, filed Junell, Laplume.

The present invention relates to teaching machines,'and moreparticularly to such machines in which instructional items are presentedto a student in subdivided, or paragraph form, each item terminating ina question to which the student is to reply, to test the comprehensionof the material being taught in the instructional item. The furtherpresentation of instructional material is stopped after the question, topermit the student time to answer, the student being supplied with akeyboard or other manually operable device, such as a telephone dial,which enables the student to choose a number of different letters,numbers, or alphanumeric combinations in accordance with the reply hewishes to give in the light of the question posed.

Teaching machines in which instructional items are separately presentedto individual students have the advantage 1969, by Jacques overcomputer-type generated teaching programs that they are comparativelyinexpensive, do not require specialized programming, while quickly andefficiently providing instructional material to the students.Additionally, it is simple to check whether the student has learned thematerial presented by concluding even small steps in the teachingprocess with frequent questions. Some of these machines may be arrangedsuch that each instructional item ends by a multiple choice question,the particular choices being selected by pressing a key or dialing anumber. When the student has given the correct answer or, if desired,after a predetermined number of erroneous answers has been recorded, themachine may give a complete correct answer in clear language, then toresume further instructional item in accordance with a recorded text.The correct and incorrect answers can be automatically counted. Still,the interplay between student and teaching machine is only inrudimentary form.

It is an object to improve the capability of interchange of informationbetween student and a teaching machine and to enable the student tointroduce replies into the machine in a form which is more sophisticatedand complete than in prior art equipment, without substantiallycomplicating the machine structure.

SUBJECT MATTER OF THE PRESENT INVENTION Briefly, a movable record meanssuch as a magnetic tape stores instructional items thereon forpresentation to a student. The tape is read by a transducer, amplified,and presented to the student over a loudspeaker, earphones, or the like.The student has a signal input device such as a keyboard, telephone dialor the like. Upon selection of a particular key, or a combination ofkeys (or dialing of the dial) a given code is generated. Theinstructional item recorded on the tape, at the end of the item, is soarranged that the student is asked to reply to a question posed and tooperate the keyboard, or dial, to select an indication of the answer.

Besides the instructional item, the tape has recorded thereon a coderepresentative of the correct answer to be given; and further, an end ofitem signal, such as a supersonic or sub-audible frequency. As soon asthe end of item signal is detected, the earphones or loudspeaker aredisabled and the tape recorder reading head is switched over to a codestorage device which stores the code recorded on the tape indicative ofthe correct answer. When the student operates his input device, the codegenerated by the particular key, or dial movement, or combination ofkeys and dial movements, is compared with the code derived from thetape. Upon coincidence, indicative of a correct answer, the tape iscaused to move forward to the next instruction item, the correct answercan be counted, and an indication is given to the student. Uponnon-coincidence, indicative of a wrong answer, an indication is given tothe student. When a predetermined count of wrong answers is reached, thetape is then caused to proceed either to the next instruction item, orto an auxiliary instruction item which further explains the prior item,in order to give additional instruction to then elicit the correctanswer.

The principal components of the teaching machine thus are: (a) a recordreproduction system (such as a sound reproducer) to reproduce thequestions previously recorded, sense control items recorded andtransduce coded signals indicative of answers; (b) a keyboard or similardevice to act as a read-in unit, or interface between student andmachine; (c) a memory or storage device to record, after decoding, onthe one hand the coded signals from the recording medium, such as themagnetic tape, and recording the correct answers, and additionally torecord the coded signals derived from the keyboard; and (d) a logic, orcomparator circuit which compares the two recorded codes.

The invention will be described by way of example with reference to theaccompanying drawings, wherein:

FIG. 1 is a schematic diagram of the teaching machine;

FIGS. 2, 3, 5, and 7 are partial schematic diagrams of portions of theteaching machine of FIG. 1, illustrating possible alternativeconstructions;

FIGS. 4 and 6 are general, simplified schematic diagrams of two otherembodiments of the present invention; and

FIG. 8 is a schematic graph of signals appearing in the system.

In all figures, like parts have been given the same reference numerals.The machine as shown in FIG. 1 is based on sound records recorded on amagnetic tape 1. A transducer head 2 picks up signals which areconnected to an amplifier 3. The signals from amplifier 3 are connectedto normally closed (NC) contacts 4 of a relay 5 through a volume controlschematically shown at 6 to a loudspeaker, or earphone 7. Each pupilwill have an individual set of earphones.

Magnetic tape 1 has recorded thereon instruction items which terminatein a question which is put to the student. At the end of eachinstruction item, a sub-audible frequency, for example in the 70 Hzrange, is recorded on the tape. A special, low-frequency sensitiveamplifier 8 is connected to the output of amplifier 3 and provides anoutput signal which is applied to relay 5, opening the NC contacts 4 andclosing normally open (NO) contact 9. The audio transducer 7 is thusremoved from the circuit and, instead, signals derived from tape 1 arenow applied over amplifier 3 to a memory or storage element 10 which, asshown, is formed by a shift register having serial input and paralleloutput.

The end of item sub-audible frequency signal recorded on tape 1 isfollowed by signals representative of a correct answer, encoded inbinary code, and indicating a sequence, or set of alpha-numericalcharacters to form the correct answer to the question posed by thepreceding instruction item. The coding of the signals may be as desired;one simple code is the ordinary Telex" code, formed as an amplitude,frequency, or phase modulated carrier signal of acoustic frequency. Eachbit of the coded signal is recorded in a specific unit of the memory 10.

The end of item" signal is superimposed on the coded signal, to maintainrelay 5 in pulled-in position until all bits of the code recorded ontape 1 are stored in memory 10. As soon as the sub-audible signalceases, relay 5 will drop out. A source of positive voltage is connectedto contacts 11 and then to a network consisting of resistances 13, 14,and a condenser 12. The network, and the type of contact 11 are soarranged that, upon closing (or opening) of relay 11, an electric pulseA is obtained across resistance 13, due to charge (or discharge) ofcondenser 12. Pulse A controls operation of the motors which wind thetape 1. Neither the motors, nor the control by the pulse from condenser12 are shown in detail, since both are well known in the art. Suitablediodes may be inserted in the control circuit to prevent pulses ofundesired polarity from aflecting operation of the control arrangement.

When the student has listened to the instructional item and to thequestion at the end thereof, he is invited to record his answer bysuccessive, or simultaneous operation of keys on a keyboard 15.Operation of any one key produces a pulse train which, in binary code,is representative of an alphanumeric character. This pulse train isapplied to a memory 16, identical to memory 10. When the student hasentered his reply, he then operates a special button 17 indicating thatthe response is complete.

FIG. 7 illustrates in greater detail a form of keyboard and theconnections thereto. Input to shift register 60, which is connected toshift register 16 in FIG. 1, is in parallel; output is series, A set ofinputs, a, b, c, d, accept signals in a code of five digits. Operationof any one key 61, 62 of the keyboard applies a tension to preselectedlines of the set of parallel input lines. Diodes 66 are provided toavoid spurious, parallel paths and interconnection of the input linesamong each other. Thus, operation of key 61 applies tension only tolines a and e; operation of key 62 applies tension only to lines b, c,and 2. Thus, each key may correspond to a specific group of lines havinga voltage applied thereto, and another group of lines having zerovoltage, Alphanumeric characters may, thus, be transduced into binarylanguage, each key having a specific code assigned to it. Operation ofany key will provide sequences of pulses at the output of OR circuit 63.A differentiating circuit 64, connected to the output of circuit 63 thenprovides two outputs of opposite polarity, corresponding to the forwardand rear flanks of pulses derived from OR-gate 63. The first of thesedifferentiated waves is utilized to control the recording of the pulsesin register 60; the second one is utilized to start a clock 65. Clock 65supplies a pulse each for each input to register 60, for example five inthe example chosen in FIG. 7. These pulses are applied to the shiftcontrol input of shift register 60.

The output of shift register 60 will thus be a train of pulses which hasthe characteristic given by the particular key which has been operated.FIG. 8 illustrates pulse trains 61a, 62a, 65a and available at theoutputs of clock 65, and at the output of shift register 60,respectively, upon operation of the respective keys 61, 62.

The sequential pulses derived from shift register 60 are applied tomemory 16, under control of the clock pulses from unit 65, to berecorded in the various positions of shift register 16.

Similar units of shift registers 10 and 16 are connected to the twoinputs of AND-gate 18. Each output of AND-gate 18 is connected, in turn,to a multiple-input AND-gate 19. The output from AND-gate 19 thus willbe indicative of complete coincidence of all the stages of the shiftregisters l0, 16; if output from AND-gate 19 is obtained, that is, forexample, if the AND-gate output 19 would be high, indicating that allits inputs are activated, the high output will indicate that theresponse by the student is identical the code recorded on tape 1. Uponsimultaneous appearance of a high output from AND- gate 19 and operationof key 17, AND-gate 20 will be activated and have an output which willactivate a correct reply counter 21, to count the correct answers, andalso to indicate that a correct answer was given on a correctanswerindicator 21A. The indicator 21A may remain lit for apredetermined time, for example several seconds, by a delay circuitinherent therein and not specially shown. Simultaneously, a signal willbe applied to OR-gate 23, which will have an output signal M. Outputsignal M controls restarting of the motor of the tape 1 to present asubsequent item to transducer head 2, and to re-set shift register 10 tozero. The shift register 16 is re-set to zero upon operation of key 17through a circuit from key 17, OR-gate 28 to the shift register 16.

If the student supplies an answer which is different from that which isrecorded on tape 1, and decoded and fed into shift register 10, nooutput will be obtained from AND-gate 19. Operation of key 17 will,however, cause output from AND- gate 22 which, as schematicallyindicated, has an inverted input from AND-gate 19. A counter of mistakenreplies (CMR) 24 will step by one count, and simultaneously a mistakenreply" indicator 25 will be energized. The indicator 25 preferablycontains a legend inviting the student to think again and to give adifferent reply. A counter 26, likewise activated from AND-gate 22 iscaused to progress one step. If the student, after reconsideration,proposes a second incorrect answer, the same step will be repeated,counter 26 stepping a further count. When counter 26 has reached apredetermined count, for example three, it will provide an output pulsewhich is connected to OR-gate 23, again causing the previously describedoperations start of the motor to cause tape 1 to proceed to the nextitem, and re-set of memory 10. Additionally, a pulse from OR-gate 23 istransmitted back to counter 26 to re-set the counter to zero. Thus, thesystem is not indefinitely blocked if the student does not, eventually,find the correct answer. Preferably, the next instruction item containsthe correct answer to the previous item, before proceeding with furthereducational material. This is provided to the student over transducerelement 7. Button 27, and OR- gate 28 enable the student to erase,manually, memory 16 in case the student had made a mere recording erroron keyboard 15, which is discovered before operation of key 17.

In accordance with a feature of the invention, the text of theinstruction item and the coded signal which identifies the correct replyis superimposed on the same track of the magnetic tape. Each codedsignal is formed as an amplitude, phase, or frequency modulated signalon a carrier having a carrier frequency beyond the frequency spectrumallocated to the instructional item. For example, without detractingfrom the in telligibility of the text, the frequency band of the voicerecording of the instructional item can be limited to about 3,000 Hz;the coding signals can then be recorded on a carrier having a frequencyjump from 4,000 to 5,000 Hz. Thus, it is simple to isolate a code of alowest frequency of 4,000 Hz from speech frequency of 3,000 Hz and belowby means of a frequency filter which attenuates substantially allfrequencies below 4,000 Hz. The coded signal will not, moreover, bedisturbed by the recording of the text if precautions are taken to cutoff all frequencies above 3,000 Hz. Well known techniques in thecommunication field, in particular relating to carrier current systemsmay be used. FIG. 5 is a partial schematic diagram which illustrates theconnection of amplifier 3, permanently connected to a low-pass filter Fl to supply the acoustic transducer; and further, permanently connectedto a high-pass filter F2 permanently connected to the storage element,shift register 10. The "end of item" signal may be very short to take upbut little time in the running of the tape to provide for efficientutilization thereof.

The individual circuit components themselves are well known in the artand need not be described in detail; relays, logic circuits, and thelike may be constructed in any convenient manner.

Various modifications and changes may be made in the teaching machine asbasically described above. FIG. 2 illustrates a variation in which themachine is supplied with two transducer heads 2, 2A, each aligned with aseparate track on magnetic tape 1. One track is assigned to theinstructional item, the other to the coded signals identifying thecorrect answer. An arrangement in accordance with FIG. 2 has theadvantage that the time to record the correct answer in memory 10 isextended. Thus, this additional time may be utilized to add redundancybits to a code to reduce, or suppress reading errors which may ariseduring recording or reproduction. By extending the capacity of memories10 and 16, longer answers may be recorded. The comparison and othercircuits, not shown in FIG. 2, are similar to those illustrated inconnection with FIG. 1.

In the embodiment of FIG. 2, the two transducer heads 2 and 2A, shownadjacent each other, would, in actual construction, actually be one ontop of the other and arranged to read parallel tracks. The text is readby transducer head 2, connected to the input of amplifier 3, andconnected to acoustic transducer 7. The end of item" signal is detectedby the selective amplifier 8, then rectified and filtered inrectifierfilter unit 30 and then connected to an output A to control therunning motor to the tape 1 to stop. The codes which are representativeof the correct reply are read by transducer 2A and connected to memory10.

In accordance with another embodiment, an output printer is associatedwith the teaching machine. An output printer may be utilized inconnection with the embodiment of FIG. 1, as well as with that of FIG.2. The printer will print out the reply, or the successive replies ofthe student. These answers may be printed in black. The correct answer,as read from the tape, may .be printed in red. The machine may, forexample, print out the correct answer after the student has deliveredthe last reply which the machine will accept, for example the correctanswer, or the third erroneous reply, the number of replies beingdetermined by the setting of counter 26. The student thus obtains awritten record which permits comparison of his answers to those deemedcorrect by the teaching machine. The motor driving the tape is startedonly when the contents of memory are transferred to the printer.

Another embodiment is illustrated in FIG. 3, which is a variation of theembodiment described in connection with FIG. 2, that is a separate trackis utilized for the coded signals.

Keyboard is connected to one of inputs 33 of a printer 31 in such amanner that as the student proceeds to type on the keys of keyboard 15,memory 16 is filled as the answer is recorded on printer 31. Operationof key 17 again, as before, starts comparison in AND-gate 20 andAND-gate 22, respectively. Additionally, OR-gate 32 is activated tooperate the carriage return and line spacer of printer 31. The signalfrom circuit 32 does not, as in FIG. 1, control erasing of memory 10,but rather transfers the content to the printer 31 through output 34.Outputs 33, 34 are equivalent; the output applied over line 34, however,is printed in a different style, or color from that from output 33.Thus, the distinction between the answer from the student and thatsupplied by the code will become plain. A slow response relay 35controls operation of the spooling motor for the magnetic tape, asindicated by the line for signal M; additionally, OR-gate 32 has theinput from the contacts of relay 35 applied thereto to control carriagereturn and line spacing of printer 31. The delay in response of relay 35is controlled such that sufficient time is available for the memory 10to be completely emptied and supplied to printer 31 before relay 35 willrespond.

Another embodiment of the invention is illustrated in FIG. 4; the replysupplied by the student is not recorded in a memory but rather comparedstep by step as it is given with the contents of memory 10. Acommutator, or stepping switch 40, or any similar arrangement, such as alogic circuit, having a similar function, successively tests thecontents of the various stagesof memory 10. A unit 41, schematicallyindicated, steps the switch 40 in response to each pulse emitted fromkeyboard 15, upon operation of any one key. The AND-circuit 41, havingan inverted output, compares at all instances the contents of a stage ofmemory 10 with the pulses from the keyboard 15. As soon as a mismatch isdetected, a voltage will appear at the output of unit 42, causing changeof state of flipflop 43. When the student operates key 17, AND-gate 44will have an output thereat to operate the counter of mistaken replies24. If, on the other hand, there is no mismatch, AND- gate 45 (which hasan inverted input) provides an output voltage which operates counter 21of the correct replies, and the associated correct reply indicator 21A.

Embodiment of FIG. 6: Memory 10, and memory 16 are shift registershaving series inputs and series outputs. These memories are filled atthe left side, as previously described in connection with FIG. 1, memory10 receiving the codes recorded on the magnetic tape, and memory 16 thesignals from keyboard 15.

The outputs of the two memories are connected to the inputs of anexclusive-OR" circuit 50 which controls a bistable flip-flop 51.Operation of key 17 of the keyboard 15 starts a clock 52 which providesas many pulses as the shift registers 10 and 16, respectively, havestages. These pulses cause successive shifting of the data recorded inthe stages of the shift register towards the right. Circuit 50 compares,at all instances, the outputs derived from the registers. If thecontents of the registers are not identical, that is if the responsefrom the student differs from that recorded on the magnetic tape,circuit will detect the mismatch and cause change-over of flip-flop 51to its second stable state. The final state of flip-flop 51 will thus bedifferent, depending upon whether the student has supplied a correct, ora mistaken reply. The information stored in flip-flop 51 is used, asbefore, in order to control the counters of correct, and mistakenreplies, and to control the indicators connected thereto.

Register 10 is connected through a line 53 to an 0R-gate 54 so that, atthe end of the pulses from clock 52, memory 10 will again be in the samestate as when previously loaded. Thus, if the student had supplied anerroneous answer he may, thereafter, supply another one which can againbe compared with the contents of memory 10 under the same conditions asbefore.

The spooling motor, or motors of the magnetic tape causes re-set ofclock 52 to start another cycle, and further causes interruption of theconnection of line 53. Line 53 can be opened,for example, by anadditional contact on the relay controlling motor operation, and nowshown for simplicity of the drawing. In this manner, as clock 52 againsupplies shift pulses, the shift register 10 will empty due tointerruption of the re-circulating line 53 to become cleared to recordthe code indicative of the correct answer at the end of the subsequentitem.

If the student should notice that, before operating key 17, he haderroneously operated the wrong key, memory 16 can be erased by applyingthe pulses of clock 52 only to shift register 16. Operating key 55starts clock 52 while, at the same time, cutting the connection betweenclock 52 and memory 10 by opening of a normally closed contact.Flip-flop 51 is reset to its rest, or zero position after each operationof key 17, or of key 55, so that it shall always be in the rest (orzero) position before the contents of memories 10 and 16 are to becompared. A delay element, schematically indicated by unit 56, retardsre-set to zero during the time required for comparison.

In accordance with another feature of the invention, operation of onekey of keyboard 15 may control codes assigned to several alphanumericcharacters such as letters, numbers, or other signs, in accordance withthe principle well known from the ordinary telephone dial. The code sentby such an input device will have some ambiguity in the answer;nevertheless, the probability that a wrong reply will correspond exactlyto g the code for the correct answer is, as has been found frompractical experience, very small; this probability decreases as thenumber of letters required for the correct answer is increased. Such asystem has the advantage of requiring only a simplified keyboard, alesser length of code assigned to each key, and a simplified comparisondevice to compare the replies furnished by the student and the repliesrecorded on the tape. Such a system cannot, however, be readily usedwith a print-out device printing answer in clear, human recognizablelanguage.

The present invention may be combined with the features described inprior application U.S. Ser. No. 832,290, assigned to the assignee of thepresent invention, entitled Teaching Machine." In accordance therewith,if the answer supplied by the student is not correct, a sub-item, ratherthan a subsequent instruction item is displayed to the student. Suchsub-items may be recorded on auxiliary tracks, or in interlacedpositions on a single track, and are designed to guide the student tothe correct reply. The memory elements for the recorded reply, thememory elements for the response by the student, and the comparisondevices between the two replies may be constructed as described in theabove-mentioned patent application.

The present invention has been described in connection with presentationof instructional items by way of magnetic tape having recorded thereonacoustic signals, to audibly present these items to the students. Therecording medium may take other forms; and the presentation of theinstructional item to the student need not be aurally, but may takedifferent forms, and various modifications and changes may be madewithin the scope of the inventive concept.

I claim:

1. Teaching machine comprising a movable recording means to storeinstructional items thereon for presentation to a student, said movablerecording means having a magnetic track to record, in form of magneticdigital pulses in a predetermined sequence, a code indicative of acorrect answer to represent binary numbers in the predeterminedsequence;

transducer means associated with said recording means and having anoutput device providing a human recognizable output from said storagemeans, and further providing an output electrical signal representativeof the code of the correct answer;

a student operated keyboard, recording student-generated answers enteredthereon;

indicator circuits indicating correct and incorrect answers entered insaid keyboard;

a first storage circuit storing the code indicative of the correctanswer provided by said recording means;

means responsive to operation of a plurality of keys of said keyboard inthe sequence of their operation and providing coded signals arranged ina binary digital code, in which a unique number is assigned to each key,said code being similar to said recorded code, the operation of aselected number of predetermined keys in a specific sequence providing aresponse code comprising unique binary numbers in said sequence;

and comparator means comparing the code stored in said first storagemeans and the answer code provided by said keyboard, the output of saidcomparator means being connected to said indicator circuit to indicatematch and mismatch of said codes and thus correct and incorrect answersdetected by coincidence, or non-coincidence of the keyboard generatedanswer code and the recorded code, in said sequences, in said comparatormeans.

2. Teaching machine according to claim 1, including second storagecircuit storing the answer code derived from said keyboard, the outputsof both said storage circuits being applied to said comparator means.

3. Teaching machine according to claim 2, wherein said keyboard containsalphanumeric representations and an additional special key (17), saidspecial key controlling advance of said recording means, and clearanceof said storage circuits said machine including a counter means countingcorrect and incorrect answers, said special key further re-setting atleast one ofsaid counter means to zero.

4. Teaching machine according to claim 3, wherein each key, except thespecial key, is associated with a plurality of separate alpha-numericalrepresentations.

5. Teaching machine according to claim 1, wherein said instruction itemsare stored in the form of recorded sound signals on the sound track ofthe movable recording means,

and covering a first frequency band;

and control signals having a frequency outside said frequency band arerecorded on said recording means.

6. Teaching machine according to claim 1, wherein said instruction itemsare stored in the form of recorded sound 10 signals on said recordingmeans on one track thereof;

and control signals are recorded on said recording means on anotherparallel track.

7. Teaching machine according to claim 1, including human readableread-out means connected to said keyboard and havl5 ing the codedsignals applied thereto to provide a human readable output of thestudents answer.

8. Teaching machine according to claim 7, including a further inputconnected to said read-out means to apply the code delivered from saidrecord means thereto to provide, ad-

ditionally, a human readable output of the correct answer to enablechecking of the correct answer against the student's answer.

9. Teaching machine according to claim 1, including a counter means (26)connected to count correct and mistaken replies, and connected to theoutput of said comparator means, said counter, upon counting a correctanswer, or upon a predetermined number of incorrect answers having beencounted, controlling further movement of said movable recording means topresent a further instruction item to the 30 student.

10. Teaching machine according to claim 9, wherein said recording meanshas primary instruction items and secondary instruction items recordedthereon;

and said counter means, upon counting to a predetermined count ofmistaken answers, control said transducer means and said movablerecording means to provide a human recognizable output from a secondaryinstruction item.

11. Teaching machine according to claim 1, wherein said transducer meansincludes a signal-responsive means;

said recording means has a signal having a predetennined characteristicrecorded thereon indicative that the end of an instructional item hasbeen reached, said signalresponsive means responding to saidpredetermined characteristic;

and a switch-over means is provided responsive to said signal-responsivemeans, connected to interrupt interconnection of said transducer meansto the output device and connect said transducer means to said firststorage means.

12. Teaching machine according to claim 11, wherein said 50 switch-overmeans is further connected to stop continued movement of said movablerecording means.

1. Teaching machine comprising a movable recording means to storeinstructional items thereon for presentation to a student, said movablerecording means having a magnetic track to record, in form of magneticdigital pulses in a predetermined sequence, a code indicative of acorrect answer to represent binary numbers in the predeterminedsequence; transducer means associated with said recording means andhaving an output device providing a human recognizable output from saidstorage means, and further providing an output electrical signalrepresentative of the code of the correct answer; a student operatedkeyboard, recording studenT-generated answers entered thereon; indicatorcircuits indicating correct and incorrect answers entered in saidkeyboard; a first storage circuit storing the code indicative of thecorrect answer provided by said recording means; means responsive tooperation of a plurality of keys of said keyboard in the sequence oftheir operation and providing coded signals arranged in a binary digitalcode, in which a unique number is assigned to each key, said code beingsimilar to said recorded code, the operation of a selected number ofpredetermined keys in a specific sequence providing a response codecomprising unique binary numbers in said sequence; and comparator meanscomparing the code stored in said first storage means and the answercode provided by said keyboard, the output of said comparator meansbeing connected to said indicator circuit to indicate match and mismatchof said codes and thus correct and incorrect answers detected bycoincidence, or non-coincidence of the keyboard generated answer codeand the recorded code, in said sequences, in said comparator means. 2.Teaching machine according to claim 1, including a second storagecircuit storing the answer code derived from said keyboard, the outputsof both said storage circuits being applied to said comparator means. 3.Teaching machine according to claim 2, wherein said keyboard containsalphanumeric representations and an additional special key (17), saidspecial key controlling advance of said recording means, and clearanceof said storage circuits (10, 16); said machine including a countermeans counting correct and incorrect answers, said special key furtherre-setting at least one of said counter means to zero.
 4. Teachingmachine according to claim 3, wherein each key, except the special key,is associated with a plurality of separate alpha-numericalrepresentations.
 5. Teaching machine according to claim 1, wherein saidinstruction items are stored in the form of recorded sound signals onthe sound track of the movable recording means, and covering a firstfrequency band; and control signals having a frequency outside saidfrequency band are recorded on said recording means.
 6. Teaching machineaccording to claim 1, wherein said instruction items are stored in theform of recorded sound signals on said recording means on one trackthereof; and control signals are recorded on said recording means onanother parallel track.
 7. Teaching machine according to claim 1,including human readable read-out means connected to said keyboard andhaving the coded signals applied thereto to provide a human readableoutput of the student''s answer.
 8. Teaching machine according to claim7, including a further input connected to said read-out means to applythe code delivered from said record means thereto to provide,additionally, a human readable output of the correct answer to enablechecking of the correct answer against the student''s answer. 9.Teaching machine according to claim 1, including a counter means (26)connected to count correct and mistaken replies, and connected to theoutput of said comparator means, said counter, upon counting a correctanswer, or upon a predetermined number of incorrect answers having beencounted, controlling further movement of said movable recording means topresent a further instruction item to the student.
 10. Teaching machineaccording to claim 9, wherein said recording means has primaryinstruction items and secondary instruction items recorded thereon; andsaid counter means, upon counting to a predetermined count of mistakenanswers, control said transducer means and said movable recording meansto provide a human recognizable output from a secondary instructionitem.
 11. Teaching machine according to claim 1, wherein said transducermeans includes a signal-responsive means; said recording means has asignal having a predetermined characteristic recorded thereon indicativethat the end of An instructional item has been reached, saidsignal-responsive means responding to said predetermined characteristic;and a switch-over means is provided responsive to said signal-responsivemeans, connected to interrupt interconnection of said transducer meansto the output device and connect said transducer means to said firststorage means.
 12. Teaching machine according to claim 11, wherein saidswitch-over means is further connected to stop continued movement ofsaid movable recording means.